Method of making abrading-tools



UNITED STATES PATENT OFFICE.

CLARENCE EoSCoE KING, 0 WORCESTER, MASSACHUSETTS, ASSIGNOR, To NORTON COMPANY, or WORCESTER, MASSACHUSETTS, A CORPORATION OF MASSACHUSETTS.

METHOD OF MAKING ABBADING-TOOLS.

No Drawing.

To all whom it may concern Be it known that I, CLARENCE RosCoE KING, a citizen of the United States of America, residing at Worcester, in the county of more particularly to a method of making abras1ve grams tools of abrasive grains bonded together by means of vulcanized substances.

In the manufacture of a rubber bonded abrading tool, abrasive grain is' embedded in rubber and the latter vulcanized. This process. however, is not merely one of vulcanizing rubber, since it must be so carriedon that the bond will not lose its intimate Contact with the abrasive grain after vulcanization has been' completed. The adhesive forces in volved must be sufiiciently large to hold the grain in the surface of the wheel under ordinary grinding strains, and prevent its being torn out too rapidly before it can accomplish its abrading function. I I

In accordance with the methods previously used for making Such a grinding tool, sulfur is first mechanically worked into a rubber bond, andthe' mass then rolled with a quantity of abrasive grains to embed the latter uniformly in the rubber. The mass must then be compressed under hydraulic pressure in a pressordinarily heated by steam, for a period of 2 to 4 hours before vulcanization can be effected. The partial vulcanization thus effected in the press is necessary to prevent the wheel swelling, cracking or otherwise becoming defective during the final vulcanization process. "AS a result, the process has been slow, expensive and difficult to carry out. In fact, it has been generally impossible to obtain uniform vulcanization orto carry on the process to completion. Consequently the products have varied in then physlcal nature and .many of the wheels have been found defective, So that the wheel inspectorsv have been obllged to throw out a large per- It is accordingly an object of my invention to simplify and lower the cost of the manufacture of tools which are made of bonded together by a vulcanizable material, decrease matenally the time consumed in the p ess per t on, eifect Patented Oct. 18, 1921.

Application filed November 4, 1918. Serial No. 261,106.

apomplete vulcanization and otherwise provlde a feasible method of manufacturing such abrading tools, so that they will come through the process uniform in composition and gnndin characteristics, and produce better grinding results than heretofore obtalnable with tools of this type..

W1th this and other objects in View as will appear from the following disclosure my invention resides in the steps of the process as set'forth in the specification and covered by the claims appended hereto.

In the course of my experimentation, I have corrected these diffculties by varying the process as hereinafter set forth. By employing a catalytic material with the vulcanizable bond, not only is the vulcanization action accelerated but the necessity for using the heated press is unexpectedly eliminated. For such a catalytic material, I have found that the various organic rubber vulcanization accelerators which contain nitrogen in their molecular construction are adapted for this purpose. A brief review of the organic accelerators involved in this art may be found on page #190 of The India Rubber World, published'January 1, 1917. Of these materials, I find that para-nitroso-dimethylanilin, or its acid salts is best adapted for my jecting the mass at ordinary temperatures to 4 high pressure for a few minutes only, this step serving the purposes merely of com pressing the relatively loose mass to the desired density and molding it to the-proper form for use as a grinding tool.

As a specific example of my process, the following steps may be carried out in making a wheelhaving a rubber bond vulcanized by meansof sulfur or a sulfur compound. The crude rubber, the vulcanizing sulfur and the accelerating compound, which may be para-nitroso-dimethyl-anilin or its salts, are mixed together and abrasive grain intimately incorporated in the mass, in any desired sequence of steps. Any Suitable apparatusTmay be. utilized for this purpose, although Igrefer mixing rolls. Crude rubber ijspasse .repeatedly between these heavy mixing rolls, which are preferably steam then read build up the wheel.

heated to render the rubber somewhat plastie, and the vulcanizer and catalytic material are added theretoin small proportions, while abrasive grain, such as silicon carbid or crystalline alumina, is forced into the rubber by the pressure of the rolls. When the material has been sufficiently mixed and it has been rolled out into strips of uniform thickness, it may then be cut into disk form to correspond with the size of the wheel to .be made. For a thin wheel, the disks may be made up in a single layer considerably thicker than the final size, and if a thick wheel is to be made, a plurality of strips are piled one on top of the other-to These disks are then placed in an iron mold having plates adapt ed to fit closely but movably within'the mold whereby the mass may be compressed to the desired thickness.

In accordance with my invention, it is not necessary to preheat the rubber mass, although it may be permitted to retain any residual heat absorbed during the mixin operation. The mold is placed in a col press and the plates are forced inwardly under heavy pressure, such as one ton per square inch of surface, this pressure being continued for-but a few minutes. Upon removing the mold from the cold press, I fasten the plates in place by suitable means.

The mold 1s then placed in an oven heated by any suitable agency, such as steam, and the vulcanization operation is carried on in the usual manner. This operation consumes from 10 to 20 hours, after which the wheel is for truing to the correct form and size. hile I prefer to use a cold press, as above described, I may-press the material under the action of heat without injuring the product, although such a step is entirely unnecessary.

,By my inventlon, I cut down the time of it now being feasible to utilize but a few minutes of pressure whereas previously it wasted a large portion of a working day. Furthermore, by adding the catalyzer I am enabled to carry on the vulcanizing operation to completion due to the efle'ct of the pressing operation and thus obtain a uniform quality of wheel, whereas under the old method a great many second-class wheels were frequently found and had to be thrown out. The total time of the pressing opera- 1. The method of making abrading tools,

comprising mixing sulfur, a vulcanization accelerating compound, and abrasive grains .With rubber whil heating the rubber to render it more plastic, subjecting the mass to high pressure for a few minutes to shape the tool. and thereafter vulcanizing the bond for several hours in a single heat treatment,

while confining the mass to prevent deformation thereof.

comprising mixing abrasive grain with a bond of rubber, sulfur and a vulcanization accelerator, shaping the mass by compacting it in a mold under high pressure for a short time at ordinary temperatures, confining the shaped mass to prevent deformation and thereafter completely vulcanizing the bond in one heat treatment in the absence of high external pressure.

Signed at Worcester, 31st day of Oct. 1918.

CLARENCE ROSCOE KING.

Massachusetts, this 75 2. The process of making abrading tools, v 

